Oil-filled insulating bushing



Oct. 16, 1928.

G. A. BURNHAM OIL FILLED INSULATING BUSHING Filed July 2%. 1926 Patented Oct. 16, 192s;v

I 1,688,302 PATENT oFFicE.

GEORGE A. BURNHAM, or sauces, ASSACHUSETTS, assienon 'ro connrr nLEc'rRI I CAL MANUFACTURING CORPORATION, 013 SOUTH PORA'IION OF MASSACHUSETTS.

BGSTQIQ", MASSACI IUSETTS, A (JOB- OII L-FILLEID INSULATING BUSHING.

Application fil ed July 23, 1926. Serial No. 124,535.

This invention relates tohigh tension oil or compound filled insulating bushings of the type having an oil reservoir at the top.

A high tension bushing usually has one or more joints that must be maintained 'oil tight in order to maintain "the insulating property of the insulator; and-it is of ad vantage to keep down the number 01' joints through which oil may escape.

It is an object of this invention to provide an improved constructiontor an oil fillet bushing of the above type in which the necessity for an oil seal at the top of the outer porcelain tube is obviated; andmore specifically to providea bushing of this typehaving means to indicate the level'or" the oil in the. bushing, which oil level is arranged to be below the top of the outer porcelain shell;

It is a furthersobject of the invention to provide an indicating device for an insulating bushing whichwill give visible evidence of the operating temperature of the interior'of the bushing. v I N i A further object is generally to improve thejconstruction and performance of oil filled bushingjtype insulators.

Fig. 1 is an elevation, partly in section, of.

an insulating bushing embodying the in vention; f

Fig..2 is a sectionalielevation of the top of the insulator of Fi 1 showing the oil reser voir and indicating device.

Fig. 3 is a section on the line 3-3 of Fig. 2;

Fig. 4 is a section on line4 4 of Fig. 2. 1 As here. shown, the insulator embodying the invention includes an outer porcelain casing, or shell, of substantial length which comprises an, upper section 10, am'iddlesection 12, and a lower section 14. Said upper section 10, and said middle section 12 of the outer casing have: straight cylindrical side walls 16 which are provided externally with a series of uniformly spaced capes, or petticoats 18, as iscustomary with insulators for outdoor-use. Said lowershel-l section 14 has tapered cylindrical side walls 20 which con tract at the bottom to a relatively small axial assa e. in the bottom-of the casin Said p b r:

walls 20 are'provided' with external surface corrugations 22 in the usual manner to reduce surface leakage'at that end of the in sulator. I, 1 i

Said miter casing adapted in. contain body of insulating oil or other electricallyinsulating fluid and consequently means with which this invention is not specifically coni cerned has been provided to render the joints between the several sections thereoffluidtighti V A' conducting stud 26 is disposed in the axial passage through said shell and is fixed and providev a fluid-tight seal at the bottom of the insulator. No difliculty is encountered in making this joint tight because of the relatively small area of the passage at the lower end of the insulator. g

' In accordance with this invention a metal bushing 32 having an outstanding annular flange 34 is disposed within the openv upper end of said shell section 10 and is spaced annularly theretrom and is secured thereto by a body of cement 36 which is disposed between said bushing and'shell; Said bushwhich is internally screw-threaded to receive athinmetal'cylinder .40 having slots or Win -dows 41 .at intervals about its, circumference. A. glass cylinder 44 is received on a yielding -wa'sher 42 carried by said bushing and surrounds said 'cylinder'40 and is spaced there'- from by the upstanding flange 38. A cap 46 forms the closure for theopen top of said cylinders 40 and 44. Said cap is pro vided with an annular depending flange 48 which is internally screw-threaded removably to engage the upper end of said metal cylinder 40. A yielding packing is disposed in the "annular groove formed by theouter depending rim 50. of said cap and said flange 48 to receive the upper edge of said glass cylinder 44 and provide a weather-proof jointat the top of said cylinder. "Said cap 46 is further providedfwi'th an upstanding neck 52 having an "ing has an upstanding annular flange 38 axial movement in the passage tfi-ef said. cap,

whereby to prevent injury to'the porcelain shell due to expansion of the stud.

A terminal cap 56 is screw-threaded on said stud 26 at its upper end and said cap has a reducer screw-thre: led end portion 58 which forms a terminal send for toe insulator. Said terminal cap is also provided with an annular apron 60 which depends in spaced relation about said neck 50 and forms a weatherproof covering for the passage 53 through said neck 52. The cap and stud may be pinned removably in the aforesaid relation by a pin 64.

A number of concentric tubes 65 of insulating material are provided within the outer casing and about the conductor which tubes are adapted to be paced apart by suitable means to divide the space etween the stud 26 and the outer she-ll into a number of annular intercommunicating oil-containing compartments. The insulating fluid is arranged to ill said outer shell and occupy the spaces, or compartments, between said inner insulating tubes 65. The supply of oil in the bushing must not be allowed to diminish since a large part of its insulating properties would be lost; hence it has been customary to maintain the level of the oil at a point well above the top 0." the outer shell in a transparent cylinder so that the level of the oil would be visible. This arrangement necessitated a fluid-tight joint at the top of the outer shell.

According to my invention, I provide a construction making it unnecessary to have a fiuid-tight seal at the top of the insulator. In carrying out this provision, the oil level in the insulator is maintained at a point below the top of said outer shell and below the top of the cement connection between the flange 3 and the insulator. Since the connection thus is not under oil pressure, no especial means need be provided to maintain the connection coil tight, as has been the case heretofore. Since the oil levelis below the top of the insulater, means is provided to indicate externally the condition of the oil level in the insulator. i

Said means includes a hollow metal toroidal float-member which is disposed loosely about the conductor within the insulator and is adapted to float in the oil therein and rise and fall in accordance with variations of oil level, being guided in such movements bythe conductor. Said float member is fixed to the lower end of a tube 72 which is loosely disposed to slide freely on the conductor and the upper end of said tube is. terminated, with normal oil level, intermediately within the ends of the shell 40. A thin disc 74 is fixed to the upper end of said tube and is freely movable in said shell and comprises an indicator to make known, by inspection through the glass shell 44 and the apertures 41,the relative positions of the float and consequently the level of oil in the insulator. The appearance of the disc within the middle portion of the glass shell may indicate the normal level of oil in the insulator.

The oil level within the insulator is adapted to rise and fall in accordance with tempera ture variations of the insulator and the Heat and disc may serve also as a temperature indicator for the insiilator. The glass shell 1r y be provided with indication-niarhs 76 which may cooperate with the disc T l: to maize known th combined temperature and oil-level conditions within the insulator. The highest mark may int ate a dangerously heated condition of the insulator, at or above which the insulator Hlc y break down.

The insulator is provided with an annular supporting sleeve 82 intermediate its ends by which the insulator may be secured to the easing Sal of an electrical apparatus, or other support.

A thin sheet metal cup 78 is disposed within the upper end of the insulator and is secured in place by an outstanding flange 80 thereof, which flange clamped between the sleeve 32 and the shelllO. Said cup is extended substantially beneath said float and is adapted to hold it from undue movement on the conductor when the insulator is dry or has insufficient oil therein, although the cup is not intended to limit the free movement of the float within its intended range of movement.

I claim: i

1. An insulating bushing having the combination of an oil-containing insulating shell, a conductor disposed in the oil in said shell, and an oil-level indicator including a float-member disposed within said shell in the oil thereof and having a sliding connection with said conductor.

2. An insulating bushing having an outer open top porcelain casing adapted to contain oil to some level beneaththe open top thereof, a stud disposed within said casing, an oil indicating means slidable on said studand including a tube surrounding and slidable on said stud, a float secured to the lower end of said tube, and a pointer carried by the upper end of said tube, the upper end of said tube and said pointer arranged normally to extend above the open top of said casing.

3. An insulating bushing having a cylindri'cal outer shell including an opaque insulating tube and a separateupper transparent tube connected with said insulating tube, a body of oil disposed Within said shell and be low the top of said insulating tube, and fluidgovc1'ncd means within said transparent tube arranged to indicate the level of the oil in said shell. i

l. An oil filled bushing having an outer porcelain tube, a transparent chamber on the top of said tube, a body of oil disposed within said porcelain tube and below the top thereof, and fluid-level indicating means in said chamber actuated by the oil in said tube,

5. An insulating bushing comprising an outer open top porcelain tube adapted to con tain a body of oil to some level beneath the top thereof, a metal cylinder'having cutaway portions connected with and disposed on the open top of said porcelain tube, a glass cylinder concentric with said metal cylinder, an axial, stud disposed within sald porcelain tube, an annular float surrounding said stud and adapted to be buoyed up by the oil within said tube, and fluid-level indicating-means governed by said float arranged for vertical movement on said .stud and having a compouent which is visible within said metal cylinder.

6. An oil filled insulating bushing comprising an outer open top insulating shell, a casing which has a transparent portion oined to the top of said shell, an axial stud disposed within said shell, a body of oil contained within said shell to a level which isbelow the joint between said shell and casing, and a float-member floating on the oil and having a pointer located within said transparent casing.

7. An insulator including an opaque outer;

insulating shell adapted to contain oil to some level beneath the top thereof, a conducting stud disposed within said shell, and an oillevel indicating device contained within said shell, and including a tube slidably dis posed on said stud, a float secured to the bottom-of said tube and adapted'to be buoyed up by said oil, and an indicator carried by the tube above the top of said shell.

8. In an electric insulator the combination of an insulating tube, a transparent cylinder disposed on the top of said tube, a conducting stud disposed within'said tube and extended through said cylinder, a metal cup contained within said tube mainly below the."

open top thereof and having'a fluid passage through its bottom, a body of oil contained within saidtube entirely below the open top thereof and partly filling said cup, a float disposed freely within said cup, and an indicator secured to said float and project ing into said cylinder.

9. An oil-filled type insulating bushing GEORGE A. BURNHAM. 

